Cytotoxic effects of autoxidative glycation

Incubation of the RNA phage Q beta at 37 degrees C with a mixture of 100 mM ribose and 10 microM CuSO4 resulted in a complete loss of viable phage after 20 min. This cytotoxic effect required both ribose and cupric ions. There was a direct correlation between the decrease in the percentage of phage survival and: (a) the length of incubation, and (b) the concentrations of both ribose and CuSO4. Addition of the strong chelator diethylenetriaminepentaacetic acid abolished the cytotoxic effect. These results are consistent with an initial production of superoxide free radicals by transition metal catalyzed autoxidation of ribose and Amadori products, followed by dismutation of superoxide to hydrogen peroxide and generation of lethal hydroxyl radicals by the Fenton reaction. RNA isolated from phage incubated with ribose and CuSO4 retained its infectivity, suggesting that the cytotoxic effect may be mediated by a free radical attack on proteinaceous components of the phage through a site specific generation of hydroxyl radicals on protein-bound transition metal ions.